1994 Chevy S10 transmission and brakes

Hi, I have a 1994 Chevrolet pick up truck, with two wheel drive and a automatic transmission.
I’m having trouble getting the truck go from drive to reverse. It feels like it is in neutral when it should be reversing.
I also just put new brakes on it and they are starting to squeak.
So what do you think is wrong with it and how much do you think it will cost to fix it?

@Kitty239 the first thing you do is check the ATF. Is the fluid level good? Does it smell burnt?
How many miles?
As far as the brakes go, is the noise coming from the front brake pads? Or the rear brake shoes?
If the front brake pads are noisey, put some brake paste on the backing plates.
Can we assume you personally did the brake job?

Hi, thanks for replying. The ATF is good, and I just put two quarts of fluid it because it was low, but it doesn’t smell burnt. It has 124,000 miles on it.
I thought that maybe something the the transmission is slipping.
The brake noise is coming from the front and I had a car repair garage that I trust put the new brakes on. After I started to hear the noise coming from the front brakes I had them looked a different garage. They said the brakes look normal, but they’re still noisy .

The reverse could be the linkage or a blown seal in the transmission.

If it had a blown seal that means the transmission fluid could leak, right?